Ground detector



Sept. 21,1926. 1,600,402

L. P. DELSASSO El' AL GROUND DETECTOR Filled Nov. 2l. 1921 2 Sheets-Sheet 1 Sept. 21 ,1926. 1,600,402

1 P. DELsAsso ET A1. V

GROUND DETECTOR Filed Nov. 21, 1921 2 Sheets-Sheet 2 Patented Sept. 21, 1926.

UNITED ASTATE-,is PATE NTOFFICE.

` LEO y. nELsAsso, BENJAMIN F. DENGLEIQAND EDWIN R. sTAUrFAcHER, OE Los `SOUTHERN CALIFORNIA'EDISON COMPANY,

ANGELES, CALIFORNIA, AssIGNORs To A 'CORPORATION OF CALIFORNIA.

` GRoUNn DETECTOR.

Applicationled November 21, 192'1. Serial No. 516,632.

'ily understood that the;y detector lis not at f limited to such a circuit, and` owing description itjwill be, easily apparent to those skilled in the art all necessarily from the fol hou7 the detector may be applied toy other x systems. y l f The detector'herein described utilizes theY unbalanced voltage` `to `ground produced when one or morevof the transmission or distribution line wires becomes partially or totally grounded, and is so constructed that the attendants at a station are immediately notified upon the occurrence of an accidental ground by the ringingof a bell,"andA ofthe phase and character of `said ground by means of a visual indicator. vFrom these indications it can be ascertained what circuit phase, and wire is affected, thus greatly facilitates the quick location of the ground` and repair Vof the line. Thus, such a detector is of very great value to power andl lighting companies, particularly Where the transmission and distribution systems are large and complicated.

In order to give a complete understanding of the invention it will be best first to give a specific description `of the now preferred v Y form of detector that embodies the' invention. VFrom thisl description the invention, as a whole, .will'be readily understood "by those skilled in thei art', andthe objects and corresponding;accomplishments of the in# vention @Will'be best understopglinthis mam ner. For the purposel of so `describing av specific and preferred form of the invention, we now refer particularly to the accompanying drawings in whichf tor;

Fig. 2 is a rear face View of the same; Fig. Sis anl enlarged fragmentary section taken as indicated by line 3 3 lon Fig. `1; Fig. 4 isa further enlarged detail section taken'ras indicated by linea- 4; of Fig. 3;- y

and

Figs is' ii iiiiigriiiil illustrating die` eige trical connections of the detector. c

As Will'be readily understood, when'the Fig. 1 is a front face View of the detecgeneral' nature of the invention is fully-nirr derstood rfrom this description, the nieclianical make-up of the detector mechanism may befvaried a great deal; and-the mechanical arrangementthat we herein ldescribe is only al simple and convenient preferred arrange-l ment. Itis made so as to be convenient to I mount on a switch board and for this'purpose the detector may bemounted on a suitlablebase '10 of insulating material. The base 10 may carry a circular housing- 11 with' a glass face 12 4that enclosesthe indicator parts of the detector. Mountedon the upper edge ofthe base is a :harmonic bell'13 of .standard construction and design. On the back of base 10 three small transformers are mounted, T1, T2, T3, the low voltage side of each being closed throughone of three I resistance wires W, W2, and W3, arranged in triangular formation, as is clearly shown in the drawings Fig. 1. These wires are of a suitable-material and ofsuitable size-to be 'slightly heated by the current which normally Hows through them from` the` trans-I former secondary; and are selected, ras to their resistance, length and co-eiiicient of eX- pansion, so that their Variation in temperature, inl accordance with the variation of the amount of current flowing through them, will cause a substantial change in length ot the wires. The wires are lrigidlyconnectedy to the posts 15 by suitable screws 16;.and

are connected to the posts 15a, by being connected 'by screws 18 to splitV portions 17 of the posts 15".u Adjustment "screws 19r are setin the'posts 15a and bearagainst the split portions 17. These'` split portions t pushed forward by 'the adjustment screws alla' n ground.

lll

be of metal; as it will readily be seen that they connect into three independent resistance wire systems.

Suppose now, that -cycle current is iiowing in each of the three line wires L1, L2, and L3. Transformers T4, T5 and T6 will now be energized and 50-cycle potential difA ferences will exist across the secondary of each. These potential differences are at l2()o in time phase from each other in a three-phase circuit, and under normal conditons are equal in magnitude. The secondaries of these transformers are connected in delta through the O-cycie harmonic bell as can be seen in Fig. 5. Normally, therefore, there will be no 50-Cycle current through the harmonic bell. Should a ground occur on any one of the three line wires, say L1, the potential difference across transformer T4 drops and that across T5 and Ti increases in proportion to the resistance of the ground. This unbalance causes 50-cycle current to flow through the secondaries of the transformers and ring` the harmonic bell, calling the operators attention to the detector.

This same unbalance causes the current through wire 71 to decrease and allow it to cool, while that in wires l/Vz and W73 increases and allow them to expand. This moves the pointer in the direction of W1, indicating which wire is grounded and, by the amount of its deflection, the degree of Tf a ground should occur on two lines at once then the target would move in a direction between the two wires, representing the two wires partially grounded. Thus the instrument provides an audible signal, and a visual signal tothe operator to indicate which phase is affected.

lit will be seen that the sensitiveness of the instrument will depend upon several factors, among which are the distance between the pivot at 25 and the point of attachment of the connections 29, in comparison with the distance between the pivot 25 and the target T; and the amount ofrmovement in any one connecting strap 29, which last depends on such factors as the length of the wire .'W, its co-efiicient of expansion, its co-efiicient of resistance and the amount by which it normally stands out of a straight line position, as well as the current. All these various factors are in practice chosen and adjusted so that a slight ground on one of the line wires will give a distinct indication in the instrument and a complete ground on one of the live wires will not take the instrument out of its possible range of movement. y

Having described a preferred form of our invention, we claim:

1.. An instrument for detecting inequalities or equality of current flow through a plurality of wires; embodying a plurality of resistance wires .and mounting means therefor by which said resistance wires are held in a symmetrical arrangement about a common center; a spring supported pivot post at said center, an indicator arm pivotally universally mounted on said post, the center of such universal movement being to one side of the general plane of the res'stance wires and the indicator arm eX- 'tending normally to said plane; and mechanical connections between the centers of the resistance wires and the indicator arm at av point offset from its center of universal movement.

2..An instrument for detecting inequalities or equality of current flow through a plurality of wires; embodying a plurality of resistance wires and mounting means therefor by which said resistance wires are held in a symmetrical polygonall arranges ment about a Lcommon center, a spring supported pivot post at saidcenter, the end of the post being to one side of the general plane of said wires and the spring tending to move the post further away from that plane, an indicator arm universally pivotf ally mounted on the end of the post, and mechanical connections between the centers of the resistancey wires and the arm at a point removed from the universal pivot'.

Tn witness that we claim the foregoing we have-hereunto subscribed our names this 10thl day of November, 1921. p

Litio P; nnLsAsso. BENJAMIN r. DENGLER. EDWIN R. sTAUFrAoHER. 

